This invention relates to a multiple cassette record and/or playback apparatus and, more particularly, to an electronic control system for controlling the sequential operation of the various interdependent elements of that apparatus.
Magnetic tape cassettes wherein a magnetic tape is stored in a self-contained cartridge are widely used in various record and/or playback devices, such an in home entertainment systems, data logging systems, dictation systems and the like. Such tape cassettes offer the advantages of greatly simplifying the loading and unloading of tape by an operator, of protecting the tape during recording and playback operations and during handling of the tape, and of minimizing the bulk of the recording and playback devices used therewith. However, since the amount of tape that can be stored easily in a typical cartridge is rather limited, there are finite limits as to the amount of information that can be recorded thereon. In an attempt to increase such limitations of recorded information, some cassette manufacturers have attempted to increase the length of tape stored in a cassette. Nevertheless, in many applications, it is desirable to record and/or play back information substantially continuously for a length of time that exceeds the capacity of a given cassette.
Accordingly, there have been proposals for automatic cassette-changing devices whereby a multiple of tape cassettes can be automatically loaded individually and successively onto a record/playback deck to permit an operator to record or reproduce substantial lengths of information. In one proposed automatic cassette changing device, described in U.S. Pat. No. 3,821,806, a plurality of cassettes are stored in drum-like configuration and are retrieved individually to be loaded onto a record/playback deck and then returned to the storage drum. This proposed device requires a relatively complex mechanical structure for the retrieval, loading, unloading and return of cassettes.
In another proposed automatic cassette changer, such as described in U.S. Pat. No. 3,752,485, a plurality of cassettes are stored in a magazine of a type that is commonly found in photographic slide projector apparatus. As the magazine is indexed, individual cassettes are sequentially "pushed" from their storage compartments by a pushing arm and loading onto a record/playback deck. After information is recorded on or reproduced from the loaded cassette, it is returned to its storage compartment by the pushing arm and the magazine then is indexed to enable the next cassette to be retrieved. A similar magazine-type cassette-changer is described in U.S. Pat. No. 3,860,964. These types of cassette-changing devices require a relatively complex mechanical construction and, moreover, are subject to various malfunctions, such as cassette jams, during loading and unloading operations. Moreover, if used to record information thereon, it may be difficult to withdraw recorded cassettes from the magazine until the full complement of cassettes have been used.
In a further proposed automatic cassette-changer, such as described in U.S. Pat. No. 3,756,608 or in U.S. Pat. No. 3,758,122, a plurality of cassettes are stored in a magazine in stacked configuration, and individual cassettes are loaded onto a record/playback deck and thence into an output magazine, also in stacked configuration. As described in U.S. Pat. No. 3,756,608, the record/playback deck is disposed beneath the input stack and a movable platform lowers the cassettes from the input stack onto the deck. After a recording or playback operation, the platform is raised and a "pusher" pushes the cassette from the platform into the output magazine. In U.S. Pat. No. 3,758,122, the deck is positioned intermediate the input and output magazines and a feed plate pushes the lowermost cassette from the input magazine onto the deck and thence into the output magazine. The use of mechanical "pushers" or feed plates is undesirable because of a susceptibility to jam the cassettes during a loading and/or unloading operation. Furthermore, since the next succeeding cassette cannot be loaded onto the deck until the immediately preceding cassette is fully unloaded by the mechanical "pusher" or feed plate, these automatic cassette-changers are relatively inefficient. That is, since these changers are not capable of loading a cassette simultaneously with unloading a cassette, a significant amount of time is required for a complete unloading/loading cycle.
Another disadvantage of automatic cassette-changer devices of the type described above is that the progress of the various interdependent operations, such as cassette-loading, recording or playback and cassette-unloading, is not monitored. Furthermore, most of these devices do not adequately control or synchronize successive operations. For example, some of these prior art automatic cassette-changers rely upon mechanical elements, such as timing cams, or the like, to initiate and drive the various changer elements. Accordingly, there is the strong possibility that, in the event of a minor malfunction in one portion of the apparatus or the event that a particular operation is delayed slightly or instituted prematurely, a serious jam or other malfunction can occur resulting in substantial damage to the cassette-changer.